The fixing of a superstructure onto an implant is traditionally effected by direct contact between the parts, i.e. without any intermediate elements suitable for separating the respective contact surfaces. Any stress on the superstructure, generated in particular by mastication, is consequently discharged directly onto the implant and therefore also onto the bone sustaining it. The stress peaks transmitted onto the contact surface between the bone and the implant are, however, particularly detrimental as they can cause the detachment of the implant from its seat and consequently instability of the prosthesis, with a possible loss of the implant.